Generally described, a wide variety of keyboards are utilized for signal generating functions, generating data entry terminals, and remote control terminals. Typically, each key of each key assembly of the keyboard corresponds to a particular alphanumeric, such as a specific numeral, character, letter, or operation. Often the key assemblies are complex in construction and operate not only to make switch contact, but to provide an operator with a tactile sensation or feedback. Such key assemblies employ a wide variety of structures ranging from spring loaded switches to dome-type switches to provide this tactile feedback signal.
Although the above-described keyboards are effective for data entry, they offer a distinct disadvantage in that they are a source susceptible to the spreading of infectious agents, resulting in the contamination or infection of the user. Moreover, the keyboards include numerous crevices where grime and infectious agents can reside. Further, these crevices, such as the area between adjacent keys, make the keyboard hard and/or impractical to clean, since a cleaning cloth or tool may be difficult or impossible to operate between adjacent keys and any cleaning solvent used may pass between adjacent keys and contact the electronics of the keyboard, thus damaging the keyboard.
Keyboards are frequently used in work areas in the presence of infectious germs and other hazardous materials. Keyboards and other equipment in these environments often must be cleaned at regular intervals to reduce the risk of spreading disease and infection. These cleaning intervals can be set to a variety of conditions, including a predetermined period of time or a defined amount of equipment usage.
To facilitate cleaning, membrane keyboards have been developed that incorporate a substantially smooth top. Although previously developed membrane keyboards help reduce the spread of infectious diseases by providing a cleanable top surface, they are not without their problems. For instance, currently available membrane keyboards generally include key assemblies of a high actuation force and low travel length type. More specifically, actuation force is the force required to transition a key of the key assemblies from a normally raised position to a depressed position in which a signal is generated. Actuation forces are typically divided into two classifications: low actuation forces and high actuation forces. A low actuation force is generally characterized as less than about 0.3 lbf. Conversely, a high actuation force is generally characterized to be more than about 0.3 lbf.
The term “travel length” refers to the distance that the key is moved between the raised position and the depressed position. Travel lengths are typically divided into three classifications: low travel; medium travel; and full travel. Low travel is for keys which travel less than about 0.02 inches between their raised position and their depressed position. Medium travel is for keys which travel between about 0.02 inches to about 0.06 inches between their raised position and their depressed position. Full travel is for keys which travel more than about 0.06 inches between their raised position and their depressed position.
As previously developed cleanable keyboards do not have a way to alert users that the keyboard requires cleaning, the burden is on the user to keep track of the scheduled cleaning intervals. Furthermore, because the previously developed cleanable membrane style keyboards having key assemblies of the high actuation force and low travel length type, they are not suitable for touch typing (i.e., typing performed on a keyboard having key assemblies of a low actuation force and medium-to-full travel type such that a user can type with relatively no fatigue and with positive feedback of switch contact), which is preferred in most data entry terminals. Since previously developed cleanable membrane style keyboards are not touch-type keyboards, a user is unable to type for long periods of time without looking at the keyboard and/or without experiencing fatigue in his or her hands.